1. Field of the Invention
The present invention relates to an apparatus for measuring the combustion property of gas, and more particularly is concerned with electric equipment for evaluating calorific value and Wobbe index of gas being measured. The invention further relates to an apparatus for controlling the calorific value of mixed gas.
2. Description of the Prior Art
Gross calorific value and Wobbe index of gas are known as important factors indicating combustion properties of gas. Wobbe index WI is defined as follows: ##EQU1## Where Q is gross calorific value of the gas being measured, and .gamma. is the specific gravity of the gas being measured. It is understood, therefore, that the gross calorific value Q and specific gravity .gamma. are required in order to determine Wobbe index WI.
In the past, certain disadvantages have been indigenous to the technique of measurement of the gross calorific value. For example, the gas being measured is mixed with air for combustion to burn continuously under a given condition. Resultantly produced gas is taken into a heat exchanger in which evolved combustion heat is absorbed into cooling water running therethrough at a fixed flow rate. In such heat exchanger technique, the temperatures and flow rates of the gas being measured, the air for combustion and the cooling water, as well as ambient temperatures, should be kept constant, and such temperatures, flow rates and ambient temperatures are measured individually. Gross calorific value is then obtained by calculating those measured values. Such prior art generally suffers the disadvantage of requiring considerable time for the measurements to be conducted. Also the accuracies of the measurements so obtained are affected by variations in ambient conditions under which such measurements are conducted.
Another prior art aspect of gross calorific value control of mixed gas employs the above-mentioned technique wherein the gross calorific value measured is compared with a target value when they disagree, the gross calorific value of the mixed gas is controlled to coincide with the target value by changing the mixing ratio of gas components which compose the mixed gas. In this technique, therefore, it is extremely difficult to control the gross calorific value of the mixed gas accurately and quickly.
In brief, therefore, prior art systems for measurement of gas combustion properties have suffered from limited accuracy, slow speed and high man-hour costs.